Caption: Pristinamycin. Computer model of a molecule of pristinamycin, an antibiotic drug. It is classed as a streptogramin antibiotic. Pristinamycin brings a halt to bacterial growth by blocking the amino-acid links in bacterial ribosomes. This section shows the molecular surface in stick form (blue), with the Van der Waals signature - an indication of the steric size of the composite atoms - as the network of gold dots.